It would be ironic in that you were going to shoot an anemy after reading from a religious tome, which would infer a book of peace, but then you would kill an innocent. I realise one wouldn’t actually see the verse when aiming, I was speaking more figuratively than literally.
The Bible has no prohibition on honorable service up to and including killing. Killing in war is peacemaking for the US. If you missed and killed an ‘innocent’, as there was no intent, there is no condemnation. There is no irony possible for a Christian soldier in this context.